Projectile



Aug. 1, 1961 H. F, DUNLAP 2,994,274

PROJECTILE Filed June 30, 1944 INVENTOR HENRY F. DUNLAP ATTORNEY This invention relates to rotary projectiles of the type which comprises a snbcaliber core and a substantially full caliber sleeve-like member fitted closely around the core for supporting and centering it in a gun barrel and releasable from the core when the projectile emerges from the gun muzzle. More particularly, the invention has reference to a novel projectile of this type in which the sleeve-like member is released from the core by the joint action of centrifugal force and air pressure on the member when the projectile emerges from the gunmuzzle.

One object of the present invention resides in the provision of a rotary projectile comprising a snbcaliber core and a substantially full caliber supporting and centering member fitted closely around the core and expansible under the centrifugal force incident to rotation of the projectile when it emerges from the gun muzzle, whereby the member is movable longitudinally off the rear end of the core by the air pressure due to the flight of the projectile.

Another object of the invention is to provide a projectile of the character described in which the supporting and centering member has suflicient tensile strength tov hold the member together under the centrifugal force due to rotation of the projectile when it emerges from the gun muzzle, but is sufficiently elastic to expand under this force and thereby permit longitudinal movement of the member off the rear end of the core by the air pressure on the member due to the flight of the projectile.

Still another object of the invention is to provide a projectile of the character described having means mounted on the core to the rear of the supporting and centering member for positively holding the member against longitudinal displacement on the core while the projectile is in the gun barrel, the holding means being releasable from the core under centrifugal force when the projectile emerges from the gun muzzle.

An additional object of the invention is to provide a sabot projectile comprising a snbcaliber core, a substantially full caliber bourrelet fitted closely around the core and expansible under the centrifugal force incident to rotation of the projectile when it emerges from the gun muzzle, whereby the bourrelet is movable longitudinally off the rear end of the core by air pressure, and a substantially full caliber sabot mounted on the core to the rear of the bourrelet for holding the latter against longitudinal displacement on the core while the projectile is in the gun barrel, the sabot being releasable from the core when the projectile emerges from the gun muzzle.

A further object of the invention is to provide a projectile of the character described having a simple construction adapted for manufacture at low cost and in which the supporting and centering means for the core .are releasable positively from the core Without substanj tially affecting its flight stability.

These and other objects of the invention may be better understood by reference to the accompanying dravw'ng, .in which FIG. 1 is a side elevational view of one form of the }new projectile;

FIG. 2' is an enlarged longitudinalsectional view of the rear end portion of the projectile shown in FIG. 1, and

FIG. 3 is a perspective view of part of the sabot shown in FIGS. 1 and 2.

States Patent The new projectile, as shown, comprises a snbcaliber steel core 10 having an ogive 10a. A substantially full caliber bourrelet 11 is mounted on the cylindrical portion of the core to the rear of the ogive 10a, the bourrelet being in the form of an elongated sleeve fitted closely around the core. The bourrelet 11 is adapted to support and center the core 10 in the gun barrel (not shown) and is made of a material having suificient tensile strength to prevent the bourrelet from breaking apart under the action of centrifugal force due to rotation of the projectile when it emerges from the gun muzzle, as will be described in greater detail. presently. Additionally, the material from which the bourrelet 11 is made has suificient elasticity to permit the bourrelet to expand radially under this centrifugal force, so that the bourrelet when so expanded is slidable longitudinally oif the rear end of the core 10 by the air resistance on the front end of the bourrelet during the initial flight of the projectile.

At its rear end portion, the core 10 is externally threaded, as shown at 13. A substantially full caliber sabot 14 is screwed on the threaded portion 13 of the core, part of the sabot projecting forwardly from the thread 13 and engaging the rear end of the bourrelet, as shown at 15. The sabot 14 may be made of steel or other suitable material and has a plurality of longitudinal radial cuts 16 which partially divide the sabot into longitudinal segments. As shown, the cuts 16 extend radially through the sabot from the thread 13 to the peripheral surface of the sabot and extend longitudinally from the front end of the sabot to points adjacent the rear end of the sabot. It will be understood that the thread 13 is in such a direction that the rotation imparted to the sabot by the usual turning band, to be described presently, acts to tighten the sabot against the front end of the thread course on the core.

A turning band 18 is mounted on the sabot 14 intermediate its ends and is made of annealed copper or other suitable material adapted to be engraved by the usual rifling in the gun barrel to impart rotation to the projectile when it is fired from the gun. The turning band 13 may be press-fitted or otherwise mounted on the sabot and has a plurality of annular tongues 19 disposed in annular grooves in the periphery of the sabot to prevent stripping of the turning band from the sabot when the projectile is fired from the gun.

The operation of the projectile is as follows: When the projectile is fired from the gun, the powder pressure acts against the base of the core 10 and also against the rear ends of the sabot 14 and turning band 18. As the projectile moves along the gun barrel, the turning band 18 is rotated by the gun rifling, and this rotation is transmitted to the core 10 through the sabot 14 which, together with the bourrelet 11, supports and centers the core in the gun barrel. During movement of the projectile through the gun barrel, the bourrelet 11 and sabot 14- and confined by the gun barrel against radial expansion relative to the core under the centrifugal force incident to rotation of the projectile. However, when the projectile emerges from the gun muzzle, the centrifugal force due to the high speed rotation of the projectile causes the turning band 18 to break apart and causes the sabot 14 to fracture adjacent the weakening cuts 16, whereby the sabot and turning band are released from the core. Also, the centrifugal force on the bourrelet 11 causes the latter to expand radially so that it has a relatively loose lit or clearance with respect to the core 10. As a result, the air pressure on the bourrelet due to the high speed flight of the projectile moves the bourrelet longitudinally ofl the rear end of the core. Accordingly, the core 10 proceeds along its trajectory without the aerodynamic drag which would otherwise be imposed upon it by the bourrelet and the sabot.

The release of the sabot 14 and bourrelet 11 from the core is effected quickly and positively as soon as the projectile emerges from the gun muzzle. By reason of the radial expansion of the bourrelet undercentrifugal force, and its longitudinal sliding motion off the rear end of the core, the bourrelet is released from the core without creating lateral disturbing forces on the core. Also, since the bourrelet does not break apart under the centrifugal force, it does not create a wide dispersal of fragments and consequent hazard to nearby personnel.

It will be understood that while I have disclosed a sabot 1.4 which is releasable by bursting under the centrifugal force, the sabot, if desired, may be constructed so that it is expanded radially by the centrifugal force and is then moved off the rear end of the core by a sliding action under the air pressure against the bourrelet and sabot. Also, the sabot and bourrelet may be made as an integral unit which is expansible by the centrifugal force and movable off the rear end of the core by the air pressure when the projectile emerges from the gun muzzle.

While the bourrelet 11 may be made of various materials having the characteristics described above, with respect to tensile strength and elasticity, I prefer to employ a material in which the expansion under centrifugal force is dependent upon a low value of Youngs Modulus. For example, the bourrelet may be made of plastic, corolite, Bakelite, or the like. However, I have found that in the manufacture of bourrelets of this type having standard quality and characteristics, laminated phenolic resin tubing of grade C may be used to advantage. A projectile having such a bourrelet and constructed in accordance with my invention was successfully fired from a 75 mm. gun having a muzzle velocity of approximately 2800 feet per second and a rifling pitch of 25.59 calibers per turn.

The new projectile is adapted for large scale manufacture at low cost, as it has relatively few parts and may be easily assembled. If desired, the bourrelet 11 may be provided with longitudinal radial weakening cuts for facilitating expansion of the bourrelet under the centrifugal force, although it is to be understood that the bourrelet should not be weakened to the extent that it will be fractured by the centrifugal force when the projectile emerges from the gun muzzle. The sabot 14 holds the bourrelet 11 positively against longitudinal displacement on the core under setback while the projectile is in the gun barrel, but releases the bourrelet for sliding movement ofi the core when the projectile leaves the gun muzzle.

I claim:

In a rotary projectile having a subcaliber core, a substantially full caliber sleeve-like bourrelet fitted closely around the core for supporting and centering the core in a gun barrel and having a tensile strength sufiicient to hold the bourrelet together against the centrifugal force incident to rotation of the projectile when it emerges from the gun muzzle, the bourrelet having suflicient elasticity to expand radially under said centrifugal force, whereby the bourrelet is movable longitudinally off the rear end of the core by the air pressure on the bourrelet incident to the flight of the projectile, a substantially full caliber sabot threaded on the core to the rear of the bourrelet and engaging the bourrelet to hold it positively against longitudinal displacement on the core while the projectile is in the gun barrel, the sabot being at least partially seg mented by a plurality of longitudinal radial cuts, and a turning band mounted on the sabot for holding the. segments together and imparting rotation to the projectile, the sabot and band being breakable and releasable radially from the core under said centrifugal force when the projectile emerges from the gun muzzle.

References Cited in the file of this patent UNITED STATES PATENTS 132,903 Dana Nov. 12, 1872 FOREIGN PATENTS 131,034 Great Britain Aug. 21, 1919 801,218 France May 16, 1936 804,237 France July 27, 1936 

